Astroshed Guide - Explain this bit please

[Peje]

14 mins in... what is the purpose of this step in the guide. Essentially you centre any star the move vertically with altitude bolts then rotate to put in polaris' position and record the time on the RA clock.

This is the last thing I have to do before I PA so going to blindly obey but I'd like to understand what I'm actually doing.

http://m.youtube.com/?#/watch?v=4fO6hyYtPwM

Also, is there any way to know the elevation angle of polaris ahead of time? Struggling to get it inside the polar scopes field of view

Sent from my SM-G925F using Tapatalk

[brantuk]

The altitude of Polaris is your latitude on Earth. So that's what you set your mount height to. Hth

See here: http://www.astro-baby.com/simplepolar/simple_polar_alignment.htm

Then use this: http://itouchmap.com/latlong.html

[Ouroboros]

Peje - the purpose of that part of the video is to set the position of the right ascension dial to the position when Polaris transits - that is when it is at its highest point in the sky. When viewed through the polar scope that is when Polaris is at the lowest or 6 o'clock position. Polar scopes invert the image so in reality Polaris is at the highest or 12 o'clock position. As I recall it will make more sense when you watch the second video.

You don't have to use a star to do this. I did it during the day by using a black dot on a piece of paper that I fixed to point as far away as I could get it.

[Peje]

The altitude of Polaris is your latitude on Earth. So that's what you set your mount height to. Hth

See here: http://www.astro-baby.com/simplepolar/simple_polar_alignment.htm

Then use this: http://itouchmap.com/latlong.html

Thats great, thanks. Ill look at the links tomorrow on lunch

[Peje]

Peje - the purpose of that part of the video is to set the position of the right ascension dial to the position when Polaris transits - that is when it is at its highest point in the sky. When viewed through the polar scope that is when Polaris is at the lowest or 6 o'clock position. Polar scopes invert the image so in reality Polaris is at the highest or 12 o'clock position. As I recall it will make more sense when you watch the second video.

You don't have to use a star to do this. I did it during the day by using a black dot on a piece of paper that I fixed to point as far away as I could get it.

Oh that'd be brilliant. No clear skies for a few days so that will let me get this out of the way

[michaelmorris]

Personally, I love most of the the Astroshed videos.  Your link doesn't seem to work, so I'm assuming you're describing using the hour angle method for polar alignment.

As others have said, the procedure is there to set up a standard position of the polaris in the polar scope. The 'hour angle' used later is a description of how far the polarscope (i.e. the mount) has to be rotated from this standard position to give an accurate depiction of where Polaris should be in your polarscope.  This is based on your geographic location and the date and time.  Once you rotated the  axis to the correct hour angle, you then use RA and Dec adjustments of the telescope mount on it's tripod to accurately align polaris with the polaris marker in the polarscope.

[Peje]

Personally, I love most of the the Astroshed videos.  Your link doesn't seem to work, so I'm assuming you're describing using the hour angle method for polar alignment.

As others have said, the procedure is there to set up a standard position of the polaris in the polar scope. The 'hour angle' used later is a description of how far the polarscope (i.e. the mount) has to be rotated from this standard position to give an accurate depiction of where Polaris should be in your polarscope.  This is based on your geographic location and the date and time.  Once you rotated the  axis to the correct hour angle, you then use RA and Dec adjustments of the telescope mount on it's tripod to accurately align polaris with the polaris marker in the polarscope.

I totally agree his videos are great, I just didn't (and still don't) understand what I was/will be doing. Haven't had time for a proper sit down and think yet though.

Working link below (can't edit my original post)

[Peje]

Peje - the purpose of that part of the video is to set the position of the right ascension dial to the position when Polaris transits - that is when it is at its highest point in the sky. When viewed through the polar scope that is when Polaris is at the lowest or 6 o'clock position. Polar scopes invert the image so in reality Polaris is at the highest or 12 o'clock position. As I recall it will make more sense when you watch the second video.

You don't have to use a star to do this. I did it during the day by using a black dot on a piece of paper that I fixed to point as far away as I could get it.

I'm still not understanding this though, feeling a tad stupid too I must admit as it seems like it's something simple I'm not getting my head around.

So I pick an arbitrary point and put this in the dead centre of my polar scope reticule. Then using altitude bolts only to bring this downwards to the circumference of the larger circle, then rotate RA to put this in the centre of the polaris circle. How does this relate back to polaris' highest position?

[Owmuchonomy]

If you are equipped with Synscan v3.35 or higher you can use the PA routine on the handset and forget you ever had a polarscope. Works a treat as long as you are pointing to start in the vicinity of Polaris and can see two or three bright stars for the alignment.

[Peje]

Is that suitable for imaging though? That will do as a backup since my mount is only 4 months old so should be up to date.

Sent from my SM-G925F using Tapatalk

[Ouroboros]

I'm still not understanding this though, feeling a tad stupid too I must admit as it seems like it's something simple I'm not getting my head around.

No worries. Polar alignment can be tricky to get your head round. You understand do you that the aim of PA is to align the mount's RA axis with the axis of the Earth? The Earth's axis passes through an imaginary point on the sky called the celestial North Pole. The idea is to aim your mount's axis at that point. Unfortunately Polaris is not spot on the North Pole, but is about half a degree away. Polaris rotates about the celestial North Pole once every 24 hours. So to determine where the North Pole is at the time you set up your mount, you must know where Polaris is on its daily excursion about the pole. PA using the polar scope involves setting the little circle at the correct rotational position of Polaris, at the current time, and then aligning the little circle to Polaris viewed through the polar scope by adjusting the the azimuthal and declination bolts on the mount.

There are different levels of accuracy available to you for polar alignment. But it rather depends how good you need it to be. You can just set the mount approximately north, squint up the polar scope, adjust the the azimuthal and declination knobs until Polaris is somewhere near the cross in the centre of the polarscope's reticule and that'll be fine for visual observing.

The next level of alignment is to use the information from the handset telling you the position of Polaris in the polar scope. Quoting from the manual: "The LCD screen will display “Polaris Position in P.Scope = HH:MM”. It tells the orientation of Polaris in the polar-scope’s FOV. User can imagine the large circle in the FOV of a polar-scope as a clock’s face with 12:00 at the top, and put Polaris at the “HH:MM” position of the large circle when using a polar-scope to do the polar alignment. Press ENTER key to confirm and proceed to the next step. Press ESC key to return to the pre- vious step."

The next and slightly more sophisticated level of alignment is to use the hour angle of Polaris, which again the handset tells you as part of the set up routine. What you're trying to do now is part of that process to set up the mount enabling you to use hour angle. You only have to do that once once.

The hour angle is the time elapsed since Polaris last transited - that is reached its highest point as it circles the celestial North Pole. This will be the lowest point when viewed through the polar scope because the scope inverts everything viewed through it.

So, by carefully placing the little circle at the bottom you are rotating the RA axis to 00:00 hours - when Polaris transits - and then making a note of the position of the RA dial as described in the video so that you can re-set it quickly on another occasion.

Having done all this, all you need do on each occasion you polar align is use the handset to find the hour angle. Rotate the RA axis to the correct position on the RA dial, align Polaris to the little circle viewed through polar scope and that's it, done.

You can then move on to more sophisticated levels of alignment if you wish, but personally I find this is enough for imaging with shortish exposures and fine with guiding.

So I pick an arbitrary point and put this in the dead centre of my polar scope reticule. Then using altitude bolts only to bring this downwards to the circumference of the larger circle, then rotate RA to put this in the centre of the polaris circle. How does this relate back to polaris' highest position?

You are correct. Your second question is explained above. I hope this helps.

[Peje]

So, by carefully placing the little circle at the bottom you are rotating the RA axis to 00:00 hours - when Polaris transits - and then making a note of the position of the RA dial as described in the video so that you can re-set it quickly on another occasion.

To quote Gru, 'Light bulb!'

That's exactly what I was missing, thank you for restoring my sanity.

Sent from my SM-G925F using Tapatalk

[Owmuchonomy]

Is that suitable for imaging though? That will do as a backup since my mount is only 4 months old so should be up to date.

Sent from my SM-G925F using Tapatalk

It is the method of choice for imaging short of drift alignment. It is more accurate than using a polar scope.

[Peje]

It is the method of choice for imaging short of drift alignment. It is more accurate than using a polar scope.

Oh really, that sounds interesting. Must pop out and check the version.

So, and forgive me if I'm being daft, but if I didn't do this calibration with finding the exact bottom of the polaris position does it affect anything? It seems like it just another piece of info since the handset tells me the RA time to dial in each session? Or have I missed something, again!

EDIT: I think I spotted what I missed. When I get the arbitrary point to the bottom and rotate RA then I should reset the RA clock to be 00:00?

Sent from my SM-G925F using Tapatalk

[Peje]

V3.28 pretty surprised. Can these be flashed with newer fw?

EDIT: Found it. Pretty easy to do:)

Sent from my SM-G925F using Tapatalk

[Ouroboros]

It is the method of choice for imaging short of drift alignment. It is more accurate than using a polar scope.

I keep meaning to give this method another go. Every time I've tried it seems more complicated and I get bigger alignment errors than after doing a polar align. I'm probably doing something wrong.

[Owmuchonomy]

I keep meaning to give this method another go. Every time I've tried it seems more complicated and I get bigger alignment errors than after doing a polar align. I'm probably doing something wrong.

Strange, I find it so easy. I have just upgraded my mount this week and I just ran the handset routine out of the box. Haven't even taken the cap off the polarscope. After two iterations I have a polar align error of <10 arc minutes. I need a bit of error of course. I will think about making a tutorial as I am a big fan of the method as you can tell! I still drift align in PHD too but I find very little adjustment if any is required.

[Ouroboros]

Well, I probably haven't given it a fair crack. I tried it a few times, was disappointed with the result, and went back to just polar aligning. I've only ever tried it after polar aligning and it's always made it worse. But it's probably something I'm doing wrong.

Please do produce a tutorial. I'd like to give it a go.

[glowjet]

Hi PEJE,

You just might like to take a look at a Polar scope aligning query, "Polar Scope Basic Alignment" which was raised under the section "Getting Started Equipment Help and Advice" on the 27 Sept, start from thread #14. There is much explanation about the whole concept, of manual Polar alignment, some of the information you could find interesting and provide you with some answers

[Peje]

Hi PEJE,

You just might like to take a look at a Polar scope aligning query, "Polar Scope Basic Alignment" which was raised under the section "Getting Started Equipment Help and Advice" on the 27 Sept, start from thread #14. There is much explanation about the whole concept, of manual Polar alignment, some of the information you could find interesting and provide you with some answers

I understood the whole concept aside from that one piece but but thankfully the answer provided above filled in the missing blank so I was able to grasp it at last

Sent from my SM-G925F using Tapatalk

[Peje]

OK all complete and even managed to do a PA using the AstroShed method and all seemed easy enough. I guess it helped I was actually using Polaris for my calibration.

One very strange thing I noticed...

I bought the uprated altitude bolts as recommended and fitted these when I bought the mount. It seems like the lower bolt (the one with the round handle rather than the ratchet effort) seems to be too short   It is screwed in fully yet there and when if I tighten the other one up until its fully engaged then it means I'm not at the right altitude. To give some numbers..

Going by the scale I'm at  54 degrees when properly polar aligned, lower bolt fully tightened. If I tighten the other then it moves to 52 degrees before it locks. Am I doing something wrong? If not, is there a fix? Longer bolt comes to mind but those ones I bought were fairly silly money

EDIT: Mystery Solved. I am a man with a mechanical engineering degree and 15 years experience in designing complex electro-mechanical products. I am also the man that fitted the bolts the wrong way around...

[Ouroboros]

Glad you're sorted, Peje.